To provide a fuel shut-off valve 20 preventing a fuel from. flowing out to the outside even if it receives a large side wave and a wave raised from below.

This fuel shut-off valve 20 is attached to an upper part of a fuel tank FT to shut off a connection passage 32b connecting the fuel tank FT to the outside in accordance with a fuel liquid level in the fuel tank FT. The fuel shut-off valve 20 is provided with a cylindrical casing 30 forming a valve chamber 30S connected to the connection passage 32b, a float 40 stored in the valve chamber 30S and opening and closing the connection passage 32b by rising and lowering in accordance with a fuel liquid level, and a wave breaking cylindrical body 55 forming a space between an outer peripheral face of the casing 30 and it as a buffer chamber 55S and extended cylindrically down to a substantially lower end of the casing 30. The buffer chamber 55S formed by the wave breaking cylindrical body 55 draws close to a rise speed of a liquid level of the valve chamber 30S even if it receives a high wave abruptly.